Ground Improvement for the Route 21 Viaduct Project

Geotechnical aspects were critical elements of the successful construction for the Route 21 Viaduct in Newark, New Jersey. The original viaduct and interchange were structurally deficient and functionally obsolete and needed replacement. The project objective was to design and construct the replacement to the existing Route 21 Viaduct and the adjacent interchange while maintaining traffic flow throughout the construction period. Difficult subsurface conditions at the site that included a layer of weak and highly compressible layer of soft organic silt and peat complicated the construction of the project. A significant ground improvement program was required for the soft soils to permit the construction. Ground improvement was needed to reduce post construction settlements and increase the stability of the new embankments and retaining structures. The preloading program included extensive geotechnical instrumentation to control fill placement and evaluate the performance of the ground improvement. This paper discusses the ground improvement aspects of the project and presents the findings of the ground improvement program. It also highlights the key issues that affect the successful implementation of the different geotechnical aspects of the project. Design, construction and economic issues are discussed in the paper.